The conventional thongs consist of an insole that is not permeable to air or water. As a result, the sole perspiration of a foot wearing the thong is prone to accumulate between the foot sole and the insole, thereby causing various skin disorders of the foot. In addition, the insole of the conventional thongs is too rigid to give a wearing comfort to the wearer. Moreover, the insole of the conventional thongs does not provide a sufficient friction between the foot sole and the insole.